The HMRC one is accurate, it's what they use it's no different. However, they obviously give you what you would be entitled to for the remaining weeks of the financial year so you need to divide what they say by the number of weeks left to work out what you'll get a week. Then plus by the time you renew things have usually changedslightly, income slightly different etc, so it's not that it is inaccurate. I've not used entitled to.