I’ve received a gift of membership. What happens if I’m already a member?

That's fine, the membership will be added on to your existing membership. This works as follows:

1. If you're not currently a member, the gift membership starts immediately on your confirmation of acceptance;
2. If you have an annual membership active already, the gift membership starts whenever the current annual membership ends;
3. If you have an active monthly subscription, the current month will be allowed to run, and then the gift membership starts following that. The monthly subscription is paused until the year's gift ends. For example, if your monthly subscription gets billed on the 6th of each month, and you activate a gift membership on Dec 1st 2019, you have 5 days remaining of the monthly subscription. You'll therefore next be billed on Dec 6th 2020.
4. If you have an annual membership which is expiring soon, and you've set up a monthly subscription to follow it which hasn't yet been billed, the gift membership starts when the current annual one ends. The monthly subscription will start being billed at the end of the gift period. For example, if your current annual membership ends on Dec 1st 2019, the gift membership would end Dec 1st 2020 and the monthly subscription would be billed from that point.

The upshot of all that is that you can receive multiple gifts and they just add up onto each other. We won't terminate active monthly subscriptions either - they're just on pause until the end of the gift period.