Waitrose has become the second UK supermarket to reduce the price of sanitary products to cover the cost of the tampon tax.
Last month, Tesco announced it would cover the 5% tax on behalf of its customers, which will apply to tampons, sanitary towels and panty liners.
Sanitary products are currently taxed as non-essential luxury items at 5%, despite such items being a necessity.
Campaigns have been launched around the world by campaigners to push governments to scrap the tampon tax – but so far, only a handful of countries have removed the tax on sanitary products.
Kenya became the first country in the first to abolish sales tax for menstrual items back in 2004. It also ended an import duty on sanitary pads in 2011, which helped to cut costs for low-income women and girls.
In July 2017, the Mauritian government agreed to scrap the 15% tax its citizens pay on sanitary products.
Within the European Union, Ireland is unique in having zero value-added tax (VAT) on tampons, sanitary towels and panty liners. This is because the 0% rate was in place before the EU introduced its minimum rates.
Only a few other countries do not levy VAT on sanitary products, including Jamaica, Nicaragua, Nigeria, Tanzania, Lebanon and Kenya.
In 2015, Canada scrapped its national goods and services tax on menstrual products, thanks to campaigning by politician Irene Mathyssen.
New York scrapped the tax in July 2016 after Governor Andrew Cuomo signed legislation eliminating local and state sales taxes on sanitary products.
"This is a regressive tax on essential products that women have had to pay for far too long and lifting it is a matter of social and economic justice," he said in a statement.
Massachusetts was one of the five states to drop the tampon tax between 1975 and 2005, alongside Minnesota, Pennsylvania, New Jersey and Maryland. Florida, Illinois and Connecticut also scrapped the tampon tax.
Delaware, Oregon, Montana, New Hampshire and Alaska do not have sales tax and therefore don't have a tampon tax.
In January 2016, former US President Barack Obama addressed the tampon tax in an interview with YouTube star Ingrid Nilsen.
"I have no idea why states would tax these as luxury items," he said. "I suspect it's because men were making the laws when those taxes were passed."
In 2015, the French parliament voted to lower the country's tampon tax from 20% to 5.5%, bringing it in line with the UK.
In Italy, women pay a 22% tax rate on menstrual products. In Germany, the rate is 19%.