Women in England who are aged from 50 to their 71st birthday and registered with a GP are automatically invited for screening every 3 years.
But the NHS is in the process of extending the programme as a trial, offering screening to some women aged 47 to 73.
You'll first be invited for screening within 3 years of your 50th birthday, although in some areas you'll be invited from the age of 47 as part of the age extension trial.
If you want to change the appointment you have been given, contact the name and address on your invitation letter.
You may be eligible for breast cancer screening before the age of 50 if you have a very high risk of developing breast cancer.
If you're 71 or over, you'll stop receiving screening invitations.
But you're still eligible for screening and can arrange an appointment directly with your local breast screening unit.
If you do not want to be invited for breast screening in the future, contact your GP or your breast cancer screening unit and ask to be removed from their list of women eligible for screening.
You'll need to sign a form to say you do not want to be invited anymore.
If you change your mind at a later date, you can simply ask your GP or screening clinic to put you back on the list.
If you think you may have an increased risk of breast cancer because you have a family history of breast cancer (female or male) or ovarian cancer, talk to your GP so you can be referred to a hospital high-risk clinic.
The clinic may refer you for genetic testing if they feel it's appropriate.
If you have been found to have an increased risk of developing breast cancer, you may have yearly MRI scans or mammograms, depending on your age and your specific level of risk.
MRI scans are sometimes used instead of mammograms because they're better at detecting cancer if you have dense breast tissue.
NHS screening programmes care for you throughout the whole screening process, including further treatment and care if you need it.
In the case of private screening, the care and treatment you may need after screening may not be available from the provider.
You can, however, be referred back into the NHS at any time should a private mammogram be abnormal.
For more information, read the NHS leaflet Thinking of having a private screening test?