diff --git a/deploy/add_expense.sql b/deploy/add_expense.sql
new file mode 100644
index 0000000..ef4ed0b
--- /dev/null
+++ b/deploy/add_expense.sql
@@ -0,0 +1,50 @@
+-- Deploy numerus:add_expense to pg
+-- requires: schema_numerus
+-- requires: expense
+-- requires: expense_tax
+-- requires: tax
+-- requires: company
+-- requires: currency
+-- requires: parse_price
+-- requires: tax
+-- requires: tag_name
+
+begin;
+
+set search_path to numerus, public;
+
+create or replace function add_expense(company integer, invoice_date date, contact_id integer, invoice_number text, amount text, taxes integer[], tags tag_name[]) returns uuid as
+$$
+declare
+	eid integer;
+	eslug uuid;
+begin
+	insert into expense (company_id, contact_id, invoice_number, invoice_date, amount, currency_code, tags)
+	select company_id
+	     , contact_id
+	     , invoice_number
+	     , invoice_date
+	     , parse_price(amount, currency.decimal_digits)
+	     , currency_code
+	     , tags
+	from company
+	join currency using (currency_code)
+	where company.company_id = add_expense.company
+	returning expense_id, slug
+	into eid, eslug;
+
+	insert into expense_tax (expense_id, tax_id, tax_rate)
+	select eid, tax_id, tax.rate
+	from tax
+	join unnest(taxes) as etax(tax_id) using (tax_id);
+
+	return eslug;
+end;
+$$
+language plpgsql;
+
+revoke execute on function add_expense(integer, date, integer, text, text, integer[], tag_name[]) from public;
+grant execute on function add_expense(integer, date, integer, text, text, integer[], tag_name[]) to invoicer;
+grant execute on function add_expense(integer, date, integer, text, text, integer[], tag_name[]) to admin;
+
+commit;
diff --git a/revert/add_expense.sql b/revert/add_expense.sql
new file mode 100644
index 0000000..c9a600b
--- /dev/null
+++ b/revert/add_expense.sql
@@ -0,0 +1,7 @@
+-- Revert numerus:add_expense from pg
+
+begin;
+
+drop function if exists numerus.add_expense(integer, date, integer, text, text, integer[], numerus.tag_name[]);
+
+commit;
diff --git a/sqitch.plan b/sqitch.plan
index 55669a5..2b941d3 100644
--- a/sqitch.plan
+++ b/sqitch.plan
@@ -72,3 +72,4 @@ add_contact [schema_numerus extension_vat email extension_pg_libphonenumber exte
 edit_contact [schema_numerus email extension_uri country_code tag_name contact extension_vat extension_pg_libphonenumber] 2023-03-25T23:20:27Z jordi fita mas <jordi@tandem.blog> # Add function to edit contacts
 expense [schema_numerus contact company currency_code currency tag_name] 2023-04-30T13:46:36Z jordi fita mas <jordi@tandem.blog> # Add the expense relation
 expense_tax [schema_numerus expense tax tax_rate] 2023-05-01T14:08:33Z jordi fita mas <jordi@tandem.blog> # Add relation of expense taxes
+add_expense [schema_numerus expense expense_tax tax company currency parse_price tag_name] 2023-05-02T08:00:26Z jordi fita mas <jordi@tandem.blog> # Add function to create new expenses
diff --git a/test/add_expense.sql b/test/add_expense.sql
new file mode 100644
index 0000000..25e50ef
--- /dev/null
+++ b/test/add_expense.sql
@@ -0,0 +1,102 @@
+-- Test add_expense
+set client_min_messages to warning;
+create extension if not exists pgtap;
+reset client_min_messages;
+
+begin;
+
+select plan(14);
+
+set search_path to auth, numerus, public;
+
+select has_function('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]']);
+select function_lang_is('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]'], 'plpgsql');
+select function_returns('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]'], 'uuid');
+select isnt_definer('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]']);
+select volatility_is('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]'], 'volatile');
+select function_privs_are('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]'], 'guest', array []::text[]);
+select function_privs_are('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]'], 'invoicer', array ['EXECUTE']);
+select function_privs_are('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]'], 'admin', array ['EXECUTE']);
+select function_privs_are('numerus', 'add_expense', array ['integer', 'date', 'integer', 'text', 'text', 'integer[]', 'tag_name[]'], 'authenticator', array []::text[]);
+
+
+set client_min_messages to warning;
+truncate expense cascade;
+truncate contact cascade;
+truncate tax cascade;
+truncate tax_class cascade;
+truncate payment_method cascade;
+truncate company cascade;
+reset client_min_messages;
+
+set constraints "company_default_payment_method_id_fkey" deferred;
+
+insert into company (company_id, business_name, vatin, trade_name, phone, email, web, address, city, province, postal_code, country_code, currency_code, invoice_number_format, default_payment_method_id)
+values (1, 'Company 2', 'XX123', '', '555-555-555', 'a@a', '', '', '', '', '', 'ES', 'EUR', '"F"YYYY0000', 111)
+     , (2, 'Company 4', 'XX234', '', '666-666-666', 'b@b', '', '', '', '', '', 'FR', 'USD', '"INV"000-YY', 222)
+;
+
+insert into payment_method (payment_method_id, company_id, name, instructions)
+values (111, 1, 'cash', 'cash')
+     , (222, 2, 'cash', 'cash')
+;
+
+set constraints "company_default_payment_method_id_fkey" immediate;
+
+insert into tax_class (tax_class_id, company_id, name)
+values (11, 1, 'tax')
+     , (22, 2, 'tax')
+;
+
+insert into tax (tax_id, company_id, tax_class_id, name, rate)
+values (3, 1, 11, 'IRPF -15 %', -0.15)
+     , (4, 1, 11, 'IVA 21 %', 0.21)
+     , (5, 2, 22, 'IRPF -7 %', -0.07)
+     , (6, 2, 22, 'IVA 10 %', 0.10)
+;
+
+insert into contact (contact_id, company_id, business_name, vatin, trade_name, phone, email, web, address, city, province, postal_code, country_code)
+values (12, 1, 'Contact 2.1', 'XX555', '', '777-777-777', 'c@c', '', '', '', '', '', 'ES')
+     , (13, 1, 'Contact 2.2', 'XX666', '', '888-888-888', 'd@d', '', '', '', '', '', 'ES')
+     , (14, 2, 'Contact 4.1', 'XX777', '', '999-999-999', 'e@e', '', '', '', '', '', 'ES')
+     , (15, 2, 'Contact 4.2', 'XX888', '', '000-000-000', 'f@f', '', '', '', '', '', 'ES')
+;
+
+
+select lives_ok(
+	$$ select add_expense(1, '2023-05-02', 12, 'Invoice 1', '11.11', '{4}', '{tag1,tag2}') $$,
+	'Should be able to insert an expense for the first company with a tax'
+);
+
+select lives_ok(
+	$$ select add_expense(1, '2023-05-03', 13, 'Invoice 2', '22.22', '{4,3}', '{}') $$,
+	'Should be able to insert a second expense for the first company with two taxes'
+);
+
+select lives_ok(
+	$$ select add_expense(2, '2023-05-04', 15, 'Invoice 3', '33.33', '{}', '{tag3}') $$,
+	'Should be able to insert an invoice for the second company with no tax'
+);
+
+select bag_eq(
+	$$ select company_id, invoice_number, invoice_date, contact_id, amount, currency_code, tags, created_at from expense $$,
+	$$ values (1, 'Invoice 1', '2023-05-02'::date, 12, 1111, 'EUR', '{tag1,tag2}'::tag_name[], current_timestamp)
+	        , (1, 'Invoice 2', '2023-05-03'::date, 13, 2222, 'EUR', '{}'::tag_name[], current_timestamp)
+	        , (2, 'Invoice 3', '2023-05-04'::date, 15, 3333, 'USD', '{tag3}'::tag_name[], current_timestamp)
+	$$,
+	'Should have created all expenses'
+);
+
+select bag_eq(
+	$$ select invoice_number, tax_id, tax_rate from expense_tax join expense using (expense_id) $$,
+	$$ values ('Invoice 1', 4, 0.21)
+	        , ('Invoice 2', 4, 0.21)
+	        , ('Invoice 2', 3, -0.15)
+	$$,
+	'Should have created all invoice product taxes'
+);
+
+select *
+from finish();
+
+rollback;
diff --git a/verify/add_expense.sql b/verify/add_expense.sql
new file mode 100644
index 0000000..8f3ff07
--- /dev/null
+++ b/verify/add_expense.sql
@@ -0,0 +1,7 @@
+-- Verify numerus:add_expense on pg
+
+begin;
+
+select has_function_privilege('numerus.add_expense(integer, date, integer, text, text, integer[], numerus.tag_name[])', 'execute');
+
+rollback;